1. Field
This application in general relates to optical fiber laser and amplifier systems. In particular this application relates to optical fibers for laser and amplifier systems comprising highly rare-earth-doped optical fibers.
2. Description of the Related Art
Ytterbium fiber lasers with tens of watts to hundreds of watts output power have been available commercially for many years. More recently, several kW ytterbium fiber lasers operating at single transverse mode have also become available. The simple two level energy system of ytterbium with its collection of 3 lower energy levels and 4 upper levels allows efficient optical energy conversion from pump to signal in a laser or amplifier configuration.
Fiber lasers having high peak and CW powers, high repetition rates and increased stability and reliability can be advantageous in various applications. However, such lasers are difficult to develop with existing technology.